There are many things in the universe that we do not understand. And some of them are very close (on an astronomical scale, of course). The heart of our solar system - the sun - still hides many secrets. Total solar eclipses offer a rare chance to learn more about our star's unusual outer atmosphere.
Over the past century, scientists have figured out the process of a nuclear explosion that has been feeding the Sun for billions of years, learned about neutrinos that are emitted as a result of violent reactions in the core, simulated the process of energy transfer by conduction, and predicted the fate of the Sun, which will become a white dwarf in a billion years.
But the crown is something else. The thin, rarefied outer atmosphere of the Sun extends millions of kilometers beyond the photosphere - what we see and think of as the “surface” of the sun. Therefore, the corona is larger than the main body of the Sun.
The corona is so dim that it is usually completely suppressed by the light that the photosphere exudes. But during a total solar eclipse, this light is successfully blocked, and we see the moon, which is ringed by the solar halo. The crown finally has the ability to shine. If you find yourself in the USA on August 21st, you may be able to witness this amazing sight.
The temperature of the solar corona is above 1 million degrees Celsius. It is almost equal to the core temperature of the sun and is much, much hotter than the vast mass of the rest of the sun.
You wouldn't feel this warmth if you walked through the crown. The corona is incredibly thin, and its temperature is a measure of the average speed of the particles that make up it. A high temperature means a single particle will hit you at bullet speed, but if there are no particles nearby, you can barely feel the warm breeze.
So why is the corona so hot despite extending far beyond the sun's surface? Scientists don't know for sure.
Perhaps it's the magnetic fields. We know that, like a spinning ball of charged particles, the sun carries very hot magnetic energy. Magnetic fields distort and bend and can eventually burst, releasing a tremendous amount of stored energy as a result.
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Does the release of magnetic energy feed the corona? The power of energy is related to the sunspot cycle, so most likely yes. But scientists have never proven this, despite years of research and simulations.
Therefore, if you suddenly manage to personally see the plasma majesty of the solar corona in August, try to unravel the mysterious nature of our star!